Alkali metal reduction of aromatic nitro compounds

Abstract

The reaction of nitrobenzene with lithium in tetrahydrofuran gave a mixture of products consisting of azobenzene, 2-anilinoazobenzene, 2,2'-and 2,4'-dianilinoazobenzenes, anilinodibenzopyridazine, and unidentified polymeric azo compounds. Similar products were obtained from the reaction of nitrosobenzene with lithium, whereas the reaction of azoxybenzene gave exclusively azobenzene. It has been suggested that radical anion intermediates are involved in these reactions. Substituted nitro compounds react in a manner analogous to that of nitrobenzene, whereas nitroamlines are unchanged under similar conditions. Compounds such as 4-bromoazoxybenzene and 2-chloronitrobenzene undergo both deoxygenation and dehalogenation reactions on treatment with lithium in THE. 2,2'-Dinitrobiphenyl, on the other hand, gave dibenzopyridazine and a trace of carbazole on treatment with lithium in ether solvents. Under similar conditions, however, 2,2 '-dinitrodiphenyl ether did not give any cyclized product.Aromatic nitro compounds, in general, are reduced in basic medium to the corresponding azoxy, azo, and hydrazo derivatives, whereas they are converted to the corresponding amines under strongly acidic conditions or under catalytic hydrogenation.2The deoxygenation of nitro and nitroso compounds have been brought about by several reagents to give a variety of products depending on the reaction conditions and the nature of the reagents.8 Aryl nitro compounds, for example, have been reduced to the corresponding azo derivatives in fairly good yields by metal hydrides4-6 and thallium.7The reaction of nitrobenzene with sodium in liquid ammonia is very complex and may warrant further investigation.8 However, sodium amalgam has been reported to reduce aromatic nitro compounds to the corresponding azoxy and azo compounds.2 Luka-shevich® had observed the formation of mono-and disodium adducts of nitrobenzene, as well as nitrosobenzene in ether solvents. Addition of alkali metals to nitro compounds in aprotic solvents has been reported to give rise to radical anion intermediates and several groups of workers have examined the esr spectra of some of these intermediates.10 We previously examined the electronic spectra of the radical anions of a few nitrobenzene derivatives and some

Substituent effects intrans-p,p′-disubstituted azobenzenes: X-ray structures at 100 K and DFT-calculated structures

“…Compounds (I) and (II) were prepared according to literature procedures, viz. Kalyanaraman & George (1973) for (I) and Onto et al (1998) for (II). Crystals of (I) and (II) suitable for X-ray crystal structure analysis were grown from solutions in a benzene-n-heptane mixture (1:…”

Synthesis and Characterization of Electroactive Films Deposited from Aniline Dimers

“…It is well known that aromatic diazocompounds tend to show reddish hues as a result of the more extended conjugation provided by the -NvN-. 52,53 The formation of product C seems the preferred route after the incorporation of a small number of monomers to the growing chain and, consequently, its relative amount increases as the polymerization time does. In this context, it is thought that product A could be better described as an intermediate species for which the N-NЈ coupling that terminates the chain growth has not yet occurred.…”

Electron transfer reactions. Reaction of nitrones with potassium

“…The nitroso compound l l a , d in the presence of excess of potassium will lead to the azo compound 19a,d, or in the presence of excess of oxygen give the corresponding nitro compound 22. It may be mentioned in this connection that nitrosobenzene, formed as an intermediate in the reaction of nitrobenzene with lithium in THF, is converted to azobenzene in the presence of excess of lithium (10).…”